Hess, who was Adolf Hitler's deputy, died in prison after receiving a life sentence at the Nuremberg trials.

Some 500 far-right extremists began a march in Berlin on Saturday in honour of the 30th anniversary of the death of top Nazi Rudolf Hess. About 500 counter-demonstrators gathered nearby the parade in the Spandau district, separated by hundreds of heavily armoured police.

Berlin police spokesman Carsten Mueller told The Associated Press that authorities have imposed a number of restrictions on Saturday 19 August's march to ensure it passes peacefully. Police have told organisers they can march, but they're not allowed to glorify Hess, who died at Spandau prison. The neo-Nazis are allowed to bring banners: but only one for every 50 participants.

Such restrictions are common in Germany and rooted in the experience of the pre-war Weimar Republic, when opposing political groups would try to forcibly interrupt their rivals' rallies, resulting in frequent bloody street violence.

The exact rules differ according to the circumstances, but police in Germany say they generally try to balance protesters' rights to free speech and free assembly against the rights of counter-demonstrators and residents.

Openly anti-Semitic chants would prompt German police to intervene, although efforts would be made to detain specific individuals rather than to stop an entire rally, police say. Left-wing groups expect about 1,000 people to attend the counter-protests.

Hess, who received a life sentence at the Nuremberg trials for his role in planning World War II, died on 17 August 1987. Allied authorities ruled his death a suicide, but Nazi sympathisers have long claimed that he was killed and organise annual marches in his honour.

The marches used to take place in the Bavarian town of Wunsiedel, where Hess was buried until authorities removed his remains.